Police have said drivers who leave their car unattended while the engine warms up are breaking the law.

Motorists who head back inside their warm homes while their car defrosts are failing to fulfill their legal obligation to be in control of their vehicle when the engine is running, said a police spokesman.

They may also find it impossible to get insurance to pay out should a thief seize the opportunity and hop in the car and drive off.

The warnings come after England and Wales experienced the coldest night of the winter so far, with temperatures dropping as low as -9.4C (15F) overnight Tuesday and into Wednesday, according to the Met Office.

A police spokesman warned: “Anyone who needs to defrost their vehicle must ensure they stay with it and don’t leave it unattended with the keys inside.

“Drivers should always be in control of their vehicle when the engine is running, even when they’re loading or unloading shopping or baggage.

“Leaving the engine running to ‘warm up’ during the winter months not only risks having the vehicle stolen, it’s against the law.

“Don’t make it easy for opportunist thieves because they don’t even have to go to the trouble of breaking into your vehicle if you have left it running for them.

“Insurance companies may not pay out if a vehicle is stolen in this way.”

Now police are urging drivers to stay on the right side of the law - by using a de-icer, scraper or a windscreen cover.

This comes as police warn of a rise in ‘frosting’ - having your car stolen when you leave the keys in the ignition to heat it up while you scrape the windscreen.